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Full text of "Text Book Of Mechanical Engineering"

906

Appendix II.

the boiler by avoiding unequal expansion due to cold feed, and
also promote circulation.    Injectors belong to this class.

The Superheater^ as a boiler apparatus, has already been
explained.

P. 696. Fuel.  The calorific value of a given fuel can
be obtained as on p. 697, or may be expressed as a simple
formula, where the weights of other elements are given in terms
of the carbon. Thus (p. 697, lines 7 and 8) i Ib. of H produces
4-28 times the heat i Ib. of C does; and again (p. 697, line 20)
i Ib. of H must be deducted for every \ Ib. of O present.

Calorific value ir
B.T.U. per Ib.

14500 (C +4-28 (H-

where C, H, and O are the actual weights of 'these elements per
Ib. of fuel. Now as 966 B.T.U. evaporate i Ib. of water from
and at 212,

Ibs. of water evaporated per Ib. fuel =

966

given in what are called evaporation units.   For the sample on
p. 697 this would be 15*3 Ibs. of water.

A directly practical test is, however, always advisable, and for
this we may refer to Thompson's fuel calorimeter, Fig. 868. A
fuel chamber A is placed on a stand, immersed in a vessel of